Chemical additive for removing solids from a well drilling system

ABSTRACT

A chemical additive for cleaning a well drilling system and equipment includes an alcohol, preferably a terpene, and either an ether amine or a base fluid or combination of the two. The additive can be mixed with an aqueous solution that may be a water, salt or brine solution.

RELATED APPLICATIONS

This application is a continuation-in-part of Ser. No. 08/484,821 filedJun. 7, 1995 now abandoned, by Darrell P. Salisbury and Robert L. Sloanwhich is a continuation-in-part of Ser. No. 08/270,006 filed Jul. 1,1994 now abandoned, by Darrell P. Salisbury, et al., which are whollyincorporated by reference herein. A related application is entitled"Process for Removing Solids From a Well Drilling System," Ser. No.08/476,608 filed Jun. 7, 1995 by Darrell P. Salisbury and Robert L.Sloan.

FIELD OF THE INVENTION

The present invention relates to the field of completion fluids, andparticularly, to a chemical additive and process for removing sludgeparaffin and solids from a wellbore and well drilling equipment.

BACKGROUND OF THE INVENTION

The completion phase of oil and gas wells requires the use ofsolids-free completion and/or packer fluids. If solids are present inthe fluid, they can cause serious damage to a producing formation byplugging the pore spaces or the perforations and channels provided toproduce fluid flow between the formation and the wellbore. Solids in apacker fluid will eventually precipitate on a packer, making itdifficult to connect or disconnect tubing from the packer, thusresulting in a costly well workover. In order to maintain a solids-freefluid, the surface equipment, wellbore, casing, and the like, must becleaned prior to introduction of the solids-free packer or completionfluid to the wellbore.

Environmental regulations governing the disposal of oil and gas welldrilling fluids have become increasingly restrictive. Such regulationshave curtailed the use of conventional oil base muds ("OBMs"), which arebased on petroleum products such as diesel or mineral oils, and havelead to the development of synthetic base muds ("SBMs"). Synthetic basemuds are safer to the health of workers and to the environment. SBMs aremore biodegradable and more dispersible in seawater or brine, thantraditional oil base muds, however, they are more difficult to removefrom the metal surfaces of drilling equipment.

Certain solvent blends have been developed in an effort to remove SBMsduring fluid displacement and well clean up processes. However, theresidual contaminants are difficult to remove due to any entrainedsolids or metal surfaces being coated with a film of a "sticky"synthetic base fluid. In some wells solids build up on the casing.Paraffin solids in some cases contributes to this solid build-up and canbe difficult to remove.

It has been a practice to mechanically clean mud systems of residualdrilling mud by various washing and manual cleanup techniques.Mechanical cleaning, however, is not possible with respect to all of thedrilling equipment. Although the use of well drilling tools can increasethe amount of solids removed from a well casing, mechanical cleaning andwashing may not leave surface equipment clean enough to ensure that acompletion fluid will not be contaminated by residual solids.

Prior clean-up operations, typically done during the displacementprocess, made use of various surfactants and/or solvents for removingdrilling muds and cleaning drilling and wellbore equipment. U.S. Pat.Nos. 4,453,598 (Singer et al., Jun. 12, 1984); 4,474,240 (Oliver et al.,Oct. 2, 1984); 4,528,102 (Oliver et al., Jul. 9, 1985); 4,588,445(Oliver et al., May 13, 1986); and 4,592,425 (Oliver et al., Jun. 3,1986) disclose processes for chemically cleaningdrilling/completion/packer fluids.

U.S. Pat. Nos. 4,456,537 (Oliver et al., Jun. 26, 1984) and 4,515,699(Oliver et al., May 7, 1985) disclose a process for cleaning muds anddrilling systems using a surface active agent/surfactant and an alcohol.The combinations of alcohols and surfactants disclosed have a number ofdisadvantages when used with modern drilling systems, which use closedloop systems having reduced surface volume capacities of fluidsavailable for displacement, cleanup and completion purposes. Therefore,to be effective, higher concentrations of an additive or compound forremoving sludge, solids and drilling materials must be compatible withthe fluid circulated to clean the wellbore. The alcohol and surfactantcombinations disclosed cannot be used with fresh water or in highconcentrations, as it will thicken the liquid phase, thereby reducing oreliminating its effectiveness in cleaning equipment and mud solids.Moreover, the preferred alcohol disclosed, 2-ethyl hexanol, has a flashpoint below 200° F., thereby causing it to be listed as a combustibleliquid. The use of a combustible material in drilling operations isundesirable, particularly from a safety standpoint. The combinations arealso less effective in removing synthetic base muds from drillingequipment and wellbores.

SUMMARY OF THE INVENTION

A chemical additive for cleaning a well drilling system and equipment byremoving sludge, muds, mud solids, paraffin, and other well drillingresidue solids from a well bore, well drilling system and surfacedrilling equipment is provided. One formulation of the additive includesan alcohol mixed with an ether amine. A base fluid may be included withthe alcohol and ether amine. The alcohol and ether amine mixture can be40%-95% to 5%-60% be weight, respectively. The preferred alcohols arealkene alcohols, cycloalkylenes and mixtures thereof. The base fluid isselected from the group of esters, diethers, olefins, detergentalkylates and mixtures thereof.

Also, the additive may include an alcohol as described herein and a basefluid. The alcohol can be about 20%--about 75% and base fluid mixturecan be about 25%--about 80% by weight respectively.

The additive can be used undiluted or diluted with water, salt water orbrine preferably in a 1% to 25% dilution by volume. The aqueous mixtureis a dispersion of the chemical additive since the additive is not watersoluble. Hereinafter reference to an aqueous mixture of the chemicaladditive and water whether or not it is a saline solution is adispersion.

The preferred chemical additive is a mixture of an alcohol, ether amineand the base fluid. The alcohol is present at from approximately 20% to75% by weight of the additive. The alcohol may be a terpene alcohol. Thepreferred alcohol is terpinol. The ether amine is present at fromapproximately 5% to 60% by weight of the additive. The preferred etheramine is selected from the group consisting of ethoxylated ether amines,propoxylated ether amines, and mixtures thereof. The base fluid ispresent at from approximately 5% to 50% by weight of the additive. Thebase fluid is selected from the group consisting of esters, diethers,olefins, detergent alkylate and mixtures thereof.

A process for cleaning a well drilling system including drilling pits,surface equipment and the wellbore by removing sludge, muds, mud solids,paraffin and other well drilling residue solids from a well bore andwell drilling system is provided. A chemical additive including analkene alcohol and an ether amine or base fluid or combination of thetwo as described herein is prepared. The chemical additive is mixed witha desired volume of water to prepare an aqueous mixture, which isintroduced to a well drilling system. The aqueous mixture is circulatedthroughout the well drilling system, thereby removing sludge, paraffinand other solids from the well bore, casing, and other well drillingsystem equipment.

The chemical additive used in the process of the present invention maybe added to fresh water, sea water, or brine at from approximately 1% to25% by volume of the aqueous mixture. In alternate processes, 26% byvolume of the aqueous mixture up to 100% of chemical additive withoutwater can be used to clean and remove solids from the drilling system.

DETAILED DESCRIPTION OF THE INVENTION

Well drilling fluids and well systems and equipment become contaminatedwith mud weighing agents, sludge, paraffin, drill bit fines, pipe dope,solids deposited on casings, and other drilling residues. It ispreferred, and often necessary, that the well system be cleaned of useddrilling fluids and mud solids, oils, and other drilling residues aspart of the completion process. Before a wellbore is completed, the wellsystem, tubing, casing, wellbore, wellhead, and flow lines must becleaned. Once the solids and residues have been removed, a solids-freecompletion and/or packer brine can be introduced into the wellbore.After completion, it may be desirable to clean the well system.

The present invention provides a chemical additive and process forcleaning a wellbore and surface drilling equipment. In the preferredembodiment, the chemical additive is added to water to prepare anaqueous mixture which is a dispersion. Fresh water, seawater, or brinemay be used to prepare the mixture of water and additive. The chemicaladditive removes contaminating solids as previously described, such assludge, pipe dope, paraffin, mud solids, and solid drilling residuesfrom wellbore, drilling equipment, and surface equipment. The chemicaladditive of the present invention can also be used to clean mud tanks,shakers, manifolds, and the like.

An additive of the present invention includes a mixture of an alcohol in40%-95% by weight and an ether amine in 5%-60% by weight. The alcoholmay be an alkene, cycloalkylene or mixtures thereof. The additivemixture can be used in an aqueous mixture preferably from 1% to 25% byvolume additive to water. The additive may be used undiluted or dilutedat a strength of greater than 25% by volume.

Another additive is a mixture of an alcohol and a base fluid selectedfrom the group of esters, diethers, olefins, detergent alkylates andmixtures thereof. The alcohol is present from about 25% to 80% by weightand the base fluid from 80% to 25% by weight with a preferred mixture ofabout 50/50 alcohol to base fluid. The additive may be used undiluted ordiluted with water, preferably at a strength of 1% to 25% by volume ofadditive to water.

The preferred chemical additive includes a surfactant preferablyethoxylated ether amine (at from approximately 5% to 60% by weight ofthe additive), an alcohol (at from approximately 20% to 75% by weight ofthe additive), and a base fluid (at from approximately 5% to 50% byweight of the additive). Naturally occurring oils, such as low toxicitymineral oils, may be used, for the synthetic base fluid, however, suchoils are subject to more stringent disposal and handling requirementsthan synthetic fluids. In an alternate embodiment of the chemicaladditive, a propoxylated ether amine may be used for the ethoxylatedether amine. The chemical additive will be effective in cleaning andremoving the remaining drilling muds, mud solids, sludge and otherdrilling residues from the wellbore and drilling equipment whencomprising the recited compounds present in the ranges provided (percentby weight) of the total additive composition.

In the preferred process, the chemical additive will be added to waterat from 1% to 25% by volume to form an aqueous mixture. The cleaningeffects of the chemical additive will be seen where it is present in awater mixture at a minimum of 1% by volume, however, the length of timeand volume of aqueous solution required to clean a drilling system willbe decreased with the increased percent by volume of the chemicaladditive in the aqueous mixture. In other cases, 26% to 100% by volumeof the chemical additive may be used to remove and lift the drillingsolids and remaining muds from the wellbore and drilling equipment.

Ethoxylated or propoxylated ether amine is prepared by reacting primaryalcohols having a branched or straight carbon chain from C₆ to C₂₂ withacrylonitrile to form an ether nitrile. The ether nitrile is thenreacted with hydrogen in the presence of a catalyst to form an etheramine. The ether amine is then reacted with between 1 and 6 moles ofethylene or 1 to 10 moles of propylene oxide to form an ethoxylated orpropoxylated ether amine. A reaction scheme of the described compoundsto prepare the ether amine is as follows:

    __________________________________________________________________________    Alcohol Cyanoethylation                                                       ROH       + CH.sub.2 CHCN                                                                        →                                                                          ROCH.sub.2 CH.sub.2 CN                                 Alcohol     Acrylonitrile                                                                            Ether Nitrile                                          Ether Nitrile Reduction                                                       ROCH.sub.2 CH.sub.2 CN                                                                  + 2H.sub.2                                                                             →                                                                          ROCH.sub.2 CH.sub.2 CH.sub.2 NH.sub.2                  Ether Nitrile      Catalyst                                                                          Ether Amine                                            Ethoxylated Ether Amine                                                       ROCH.sub.2 CH.sub.2 CH.sub.2 NH.sub.2                                                   +                                                                                ##STR1##                                                                            →                                                                           ##STR2##                                              Ether Amine Ethylene Oxide                                                                           Ethoxylated Ether Amine                                __________________________________________________________________________

The preparation of an amine from an alcohol provides lower viscosity dueto the ether linkage. It can also have a lower specific gravity thanconventional amine products. The alcohol may be branched as opposed tolinear as with acids from fats. This is unlike the prior art, whichdiscloses using surfactants which are the amine reaction products ofmonobasic fatty acids and secondary amines.

The alcohol provides additional lifting action when coupled with theethoxylated ether amine. Thus, the additive enables greater and longerlasting lift action of sludge or other solids in a brine or other waterslurry. The alcohols are also environmentally acceptable andbiodegradable, and do not require regulated disposal practices.

In the preferred additive, the alcohol is selected from the group ofcycloalkylenes compounds known as terpenes. Terpene alcohols improvesolvency of the additive and are water insoluble. The preferred terpeneis terpinol. Other terpene related derivatives composed of carbon,hydrogen, and oxygen, and having 10 carbon atoms with 0, 1 or 2 hydroxylgroups, and 0, 1 or 2 double bonds, may be used in alternateembodiments. The hydroxyl group helps break the hydrogen bonding ofsludge to metal surfaces. The terpene alcohols are effective indispersion or emulsion systems, such as that created by the chemicaladditive of the present invention. The chemical additive breaks out ofwater and floats the solids after cleaning sludge, mud and other solidsfrom the well drilling system. Thus, making it easy to recover, removeand dispose of the contaminants from the well system.

Blends of terpenes having the provided characteristics may also be used.Any terpene blend or terpene selected should have a flash point greaterthan 200° F. A commercially available terpene product having the desiredcharacteristics is Glidsol 90 (SCM Glidco Organics, Montvale, N.J.).Also, a terpene alcohol blend, Hogsol, has the desired flash point andis suitable. (SCM Glidco Organics, Montvale, N.J.).

The combination of the ether amine and the alcohol will remove some ofthe sludges and solids from the well drilling system. Difficult toremove solids and residues such as pipe dope, however, will not beremoved by the combination. The addition of a base fluid will facilitateremoving and floating to the surface of the well bore all solids andcontaminants remaining in the well bore as a result of the drillingprocess.

The base fluid is preferably a synthetic compound selected from thefamily of compounds introduced to the drilling industry in recent years.These synthetic compounds were developed in light of increasingenvironmental regulations toward traditional oil base drilling fluids ormuds. The synthetic base fluid acts as a solvent in the chemicaladditive. The synthetic base fluid is selected as a co-solvent with thealcohol. The base fluids are generally in the size range of C₁₈ to C₂₄,and may be selected from the following compounds: esters, diethers,olefins, and detergent alkylate, as well as mixtures of the fluids.

In the preferred chemical additive, an ester will be used as the basefluid. The ester can be made by the reaction of a fatty acid with analcohol, and may be considered a synthetic vegetable oil. The ester canalso be prepared by reacting light olefins through the hydroformylation(oxo) process to form alcohols. The alcohols are then reacted with acidsto make esters. Commercially available esters which may be used toprepare the chemical additive include Exxate 1000 (Exxon, Houston, Tex.)and Exxate 1300 (Exxon, Houston, Tex.). Both products have a high flashpoint. Exxate 1000 is an acetate ester using a C₉₋₁₁ branched alcohol(oxo-decyl-acetate), and Exxate 1300 uses a C₁₃ alcohol.

Diethers made by the condensation and partial oxidation of alcohols;poly-alpha-olefin (PAO) (Ethyl Corp., Baton Rouge, La.), a straightchain non-aromatic hydrocarbon made by the polymerization of ethylene;and detergent alkylate (linear alkyl benzene LAB), composed of benzenehaving a saturated hydrocarbon attached, may be used in alternateembodiments. All the compounds are listed as nonhazardous and have flashpoints greater than 200° F. (Pensky Martin closed cup).

The following examples report the results of bench tests performed todetermine the properties and efficacy of the present invention and itsalternate embodiments. The examples are intended to be illustrative andnot limit the present invention.

EXAMPLE 1

A test was conducted to compare the cleaning efficiency of varioussynthetic base fluids, 2-ethyl hexanol, low toxicity mineral oil (LTMO),and sea water to the preferred base fluid ester when removing AmericanPetroleum Institute (API) pipe dope from steel. Pipe dope is difficultto remove from the steel of well drilling equipment. The preferred basefluid is Exxate 1000, an ester compound. The other compounds provided inTable 1 have been used in the prior art as components of completion andother well drilling fluids.

Individual 400 ml beakers were filled with approximately 250 ml of thefluids to be evaluated. The fluids were held in turbulent flow using amagnetic stir bar. A separate pipe dope coated steel coupon was loweredinto each flask of fluid and the cleaning efficiency measured. Eachcoupon was coated with approximately 3 grams of pipe dope at a thicknessof approximately 3/32 inch. Cleaning efficiency was determined as afactor of the length of time to remove a percentage of the pipe dopefrom the steel coupon.

                  TABLE 1                                                         ______________________________________                                        BASE FLUID CLEANING EFFICIENCY %, TIME (min)                                  (SOLVENT)  5          10         20                                           ______________________________________                                        2-ethyl    4          23         39                                           hexanol                                                                       Exxate 1000                                                                              15         33         57                                           Exxate 1300                                                                              14         25         46                                           WITCO 2307*                                                                              13         25         38                                           (fatty acid                                                                   ester)                                                                        LTMO       24         69         93                                           Sea water  0          0          0                                            PAO**      7          17         40                                           LAB        23         53         73                                           Petrofree***                                                                             5          14         36                                           (fatty acid                                                                   ester)                                                                        ______________________________________                                         *Witco, Houston, Texas                                                        **Ethyl Corp., Baton Rouge, Texas                                             ***Baroid, Houston, Texas                                                

The compounds tested are listed in the first column under BASE FLUID(SOLVENT) on Table 1. Cleaning efficiency as a percent of pipe doperemoved is shown for each fluid at 5, 10, and 15 minutes. The resultsreflect the solvent nature of the fluids.

The results show LTMO as having the highest cleaning efficiency. Thedisadvantage of using LTMO, however, is the required handling anddisposal of an additive containing the compound. LTMO and productscontaining it cannot be dumped offshore. Thus, extensive handling andstorage of the fluid or product containing the fluid would be required.Storage and handling capability is generally limited during a completionprocess, particularly in off-shore situations.

Linear alkylate benzene (LAB) had a relatively high cleaning efficiencyof 73% following 15 minutes of exposure to the coupon. Although this ishigher than that observed with Exxate 1000 and Exxate 1300, the use ofLAB in well drilling clean up operations is undesirable and potentiallydangerous because of the presence of low molecular weight aromatics.

Exxate 1000 was found to be the preferred base fluid because of itscleaning efficiency and non hazardous and nonhealth threateningcharacteristics.

EXAMPLE 2

The ability of the chemical additive to agglomerate and float solids tothe surface of the wellbore was simulated by laboratory bench test. Twosamples containing a 0.5 gram sample of bentonite is dispersed in 100 mlof seawater were prepared. A 4 ml quantity of the chemical additive wasadded to one sample and a 4 ml quantity of a commercially availablecleanup additive was added to the second sample. The additives wereshaken into the bentonite solution and immediately placed in a 100 mlgraduated beaker. The rise time, consistency and quality of thebentonite solids and overall appearance of the solids are reported inTable 2. The additive formulations are also shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                             SOLIDS                                                   ADDITIVE   RISE TIME REMOVED     APPEARANCE                                   ______________________________________                                        A*.sup.    1 min.    6 ml        creamy                                                                        solids                                       B**        1 min.    6 ml        creamy                                                                        solids                                       ______________________________________                                         Additive formulations:                                                        A* = Exxate 1000/Glidsol 90/Preferred Amine (25%/50%/25% by weight)           B** = 2ethyl hexanol/Witco 1017 (an amide) (50%/50% by weight)           

The results of the ability of the present invention (A) compared to acommercially available cleaning additive (B) to agglomerate and floatsolids to the surface of the wellbore show both additives to havesimilar effectiveness in removing solids from a brine solution andlifting them to the surface of the solution. The results reported inTable 2 show that following one minute of rise time (period of timefollowing shaking of the solution), 6 ml of solids were removed andfloated to the surface of each sample. The samples appeared to be creamyand smooth, comprising agglomerated bentonite and other solidspreviously present in the sea water. Although the effectiveness of bothadditive formulations in removing and floating solids to the surfacewere relatively similar, Additive B is comprised of 50% by weight of anamide. Such compounds are disadvantageous for use in cleanup processesbecause only a small volume of the compound can be used in water. If toogreat a concentration of the compound is present in water, it may form agel, thereby reducing the effectiveness of the compound as a cleanupadditive. Thus, when using a formulation similar to B, large quantitiesof water must be used in order to maintain the low dilution factor forthe amide. In cleanup situations where there are storage managementconcerns, the large volumes of water necessary for performing anadequate cleanup of the well drilling system will be difficult andpossibly prohibitive. Considerably higher concentrations of Additive A,the chemical additive of this invention, can be used therefore reducingthe volume of water and fluids which must be generated and handledand/or stored in order to perform an adequate cleanup of a wellbore anddrilling equipment.

EXAMPLE 3

The effectiveness of alternate embodiments of the present invention arereported in Table 3. The samples were prepared following the protocoldescribed in Example 2. The formulations for the alternate embodimentsare provided in Table 3. All formulations of the chemical additive weresimilar with the exception of 25% by weight of the formulationcomprising different synthetic base fluids. The terpene alcohol andpreferred amine were constant in all formulations at 50% by weight and25% by weight, respectively.

                  TABLE 3                                                         ______________________________________                                                             SOLIDS                                                   ADDITIVE   RISE TIME REMOVED     APPEARANCE                                   ______________________________________                                        C*         1 min.    6 ml        slightly                                                                      gummy,                                                                        creamy                                                                        solids                                       D**        1 min.    6 ml        creamy                                                                        solids                                       E***       1 min.    6 ml        creamy                                                                        solids                                       F****      1 min.    5 ml        slightly                                                                      gummy,                                                                        creamy                                                                        solids                                       ______________________________________                                         Additive formulations:                                                        A* = Witco 2307/Glidsol 90/Preferred Amine (25%/50%/25%) by weight)           D** = Exxate 1300/Glidsol 90/Preferred Amine (25%/50%/25%) by weight)         E*** = LAB/Glidsol 90/preferred Amine (25%/50%/25%) by weight)                F**** = PAO/Glidsol 90/preferred Amine (25%/50%/25%) by weight)          

Following a rise time of one minute, similar quantities of solids wereremoved and floated to the top of the brine solution with additives C,D, and F. Formulation F which contained the synthetic base fluid PAO,had a slightly lower volume of solids rise. The visible appearances ofthe agglomerated solids varied with formulation of the additive.Embodiments of the chemical additive containing Witco 2307 (Witco,Houston, Tex.) and the formulation containing PAO as the synthetic basefluid resulted in the solids being slightly gummy.

EXAMPLE 4

The cleaning efficiency of the chemical additive of the inventioncompared to the that of the commercially available chemical additivedescribed in Example 2 is reported in Table 4. The formulation of theadditive identified on Table 4 as (A) is 50% by weight of 2-ethylhexanol and 50% by weight of an amide (Witco 1017). The composition ofAdditive (B) on Table 4 is the preferred embodiment of the invention of25% by weight ester (Exxate 1000), 50% by weight terpinol (Glidsol 90),and 25% by weight ethoxylated ether amine. The composition of additive(C) on Table 4 is 25% by weight amide (Witco 2307), 50% by weightterpinol (Glidsol 90), and 25% by weight ethoxylated ether amine.

Steel coupons were coated with a diesel oil based drilling mud obtainedfrom a field drilling site. The mud coated coupon was immersed into a250 CM³ volume of sea water containing the various concentrations of thechemical additives described above. The samples were held in turbulentflow using a magnetic stirrer while the coupon was in the fluid. Thecleaning efficiency of the additives at the various concentrationsprovided as % in sea water, is reported in Table 4.

                  TABLE 4                                                         ______________________________________                                        ADDITIVE, % in sea                                                                        CLEANING EFFICIENCY %, TIME (min)                                 water       5          10         20                                          ______________________________________                                         4% (A)      5          8         15                                          10% (A)     10         15         25                                           4% (B)     10         15         30                                          10% (B)     20         30         65                                          10% (C)     80         95         clean                                       ______________________________________                                    

The results show that a mixture of 4% by volume of Additive A in seawater and a mixture of 10% by volume of Additive A in sea water hadsubstantially lower cleaning efficiencies than the preferred embodimentof the chemical additive, identified as (B), and Additive (C) at each ofthe reported time intervals. The mixture of 10% by volume of formulation(C) in sea water was observed to have the highest cleaning efficiencypercentage at all reported time intervals. The synthetic base fluid usedin formulation (C), however, is not suited for use in large volumes inlarge scale cleanup operations because it must be heated and meltedprior to it being used in an additive formulation. Moreover, solidslifted and separated using Additive (C) will be sticky and gummy, andtherefore, difficult to handle and effectively recover from wellbore.Following 20 minutes of treatment by additive formulation (B) present at10% by volume of the sea water mixture, a 65% cleaning efficiency wasobserved, or 65% of the mud was removed from the coupon. This percentagewould likely be improved by increased exposure time or increasedpercentage of the chemical additive (B) in the water mixture.

EXAMPLE 5

The following example is illustrative of the product and process using amixture of an alcohol and base fluid. The alcohol and base fluids arethose previously described. The preferred alcohol is a terpene, GLIDSOL90. The preferred base fluid is a fatty acid ester. The range of mixtureis 20%-75% alcohol to 80%-25% base fluid by weight. The preferredmixture is 50/50 by weight alcohol and base fluid. The additive may bediluted to 1%-25% by volume in water, sea water or brine.

The alcohol and base fluid was tested in a simulated wellbore situationgenerally described in the preceding Example 2. A comparison was made ofan additive of Glidsol 90 terpene and Petrofree fatty acid ester in a50%/50% by weight mixture and the additive designated A* which is madeof Exxate 1000/Glidsol 90/Preferred Amine in a 25%/50%/25% by weightmixture. Two types of bentonite were used; an aged regular bentonite andan aged high grade bentonite. The high grade bentonite is primarilysodium bentonite. The additives were used as 4% by volume dilution insea water.

                  TABLE 5                                                         ______________________________________                                                            SOLIDS                                                    ADDITIVE  RISE TIME REMOVED     APPEARANCE                                    ______________________________________                                        BENTONITE - REGULAR                                                           A*        2 min.     6 ml       creamy                                                                        solids                                        50/50     2 min.     4 ml       creamy                                        GLIDSOL 90/                     solids                                        PETROFREE                                                                     BENTONITE - HIGH GRADE                                                        A*        2 min.    24 ml       creamy                                                                        solids                                        50/50     5 min.    24 ml       creamy                                        GLIDSOL 90/                     solids                                        PETROFREE                                                                     ______________________________________                                    

The additive without the preferred amine did take longer for rise timeand separation on the high grade bentonite, but performed satisfactorilyin the tests.

The chemical additive of the present invention was used in a well with abuild up of solids on the casing. The chemical additive was used in an8-10% by volume in water. The chemical additive was the preferredformula A* described in Example 5 above. In the preferred process aHEDGEHOG® casing brush was used with the chemical additive to scour theinside of the casing. U.S. Pat. No. 5,419,397 covers some embodiments ofthe HEDGEHOG® and is incorporated by reference herein.

The solids were flushed from the casing. The fluid returning to thesurface was a viscous liquid. The solid material returned to the surfacewas 83% paraffin oil with a melt point of 194° F., 13% low gravitysolids (dirt, rust) and 4% water. A test on the paraffin showed that aratio of 3/1 additive to paraffin reduced the melt point of the paraffinto below room temperature.

The process for using the chemical additive in the well system can beadapted for water base muds or oil base muds. A different series ofsteps for cleaning water base muds and oil base muds is preferred. Thechemical additive is introduced into the wellbore after other fluidshave been introduced or circulated through the well system. The additivecauses the remaining drilling muds, mud solids, sludge, drillingresidues adhering to the casing, walls of the wellbore, drill bit finesand other materials to be suspended in the additive aqueous mixture andfloated to the top of the wellbore for removal. The solids can beremoved decantation, floatation, filtration or other methods known tothose skilled in the art. The chemical additive mixture can also be runthrough the surface equipment of the drilling system to remove drillingresidues from the system, thereby ensuring that any fluid introduced tothe wellbore as part of the completion process will be solids-free.

In the preferred process the hole capacity is determined and 1% byvolume of the chemical additive compared to the hole capacity is used toclean out the wellbore. The additive is diluted with water or a saltsolution to form an aqueous dispersion. A multi-phase displacement witha series of steps is used to remove the solids from the well system. Apreferred series of steps for use with a water base mud includes firstcirculating water which can be seawater through the well system. This isfollowed by the chemical additive in an 8-10% by volume to water oraqueous salt solution. After the chemical additive, a viscous spacersuch as a hyroxyethylcellulose solution was pumped throughout thesystem. Afterwards the desired completion fluids can be used.

A preferred process for removing oil base mud includes the followingsteps. A viscous spacer weighted with barite (or other weighting agents)that includes a water wetting surfactant agent is pumped into the wellfollowed by a viscous unweighted spacer with a water wetting surfactantagent. Then 15 barrels of seawater or salt water is pumped through thewell, followed by a solvent. After the solvent additional seawater ispumped. The chemical additive prepared as described herein is thenintroduced into the wellbore. Afterwards, it is preferred to use aviscous spacer with a water wetting surfactant followed by seawater orcompletion fluid.

The following is another preferred process of the use of the chemicaladditive in connection with an offshore rig cleanup operation after anSBM was used in the well. The hole capacity was 108 barrels and thedrillpipe was 3100 feet. A mixture of hydroxyethylcellulose and a waterwetting surfactant was pumped down the well. This mixture was followedby a salt solution prepared with calcium chloride. This salt solutionmay be followed by a solvent and another salt solution spacer. Thechemical additive was the prepared in an 8% by volume calcium chloridein an aqueous solution with the chemical addition as approximately 1% byvolume of the hole capacity. The circulation of the aqueous chemicaladditive solution is followed by a salt water spacer with calciumchloride.

In another rig clean up process with a hole capacity of 461 barrelsafter workstring displacement a similar process was utilized. Thecirculation of the salt water after the addition of the chemicaladditive was followed by an additional circulation of a fluid of a waterwetting surfactant and another salt water spacer.

The chemical additive used in the wellbore clean up examples describedabove is Exxate 1000/Glidso/90/Preferred Amine (25%/50%/25% by weight).The water wetting surfactants and solvents used in the clean up processare known to those skilled in the art. Also, other process steps knownin the art for wellbore cleanup may be included with additive.

It is apparent that there has been described herein a chemical additiveand process for effectively removing sludge, muds, and other solids froma well drilling system. Various changes and alterations may be made inthe practice of the chemical additive and method by those skilled in theart without departing from the spirit of this invention. It is intendedthat such changes be included within the scope of the appended claims.The present description is intended to be illustrative and not limit thepresent invention.

What is claimed is:
 1. A chemical additive for cleaning a wellbore anddrilling equipment, comprising:an ether amine having the formula;##STR3## wherein R₁ is a hydrocarbon group; R₂ is a hydrocarbon group;R₃ is an alkyl group, an alkenyl group, a hydroxyalkyl group, or anoligomer of hydroxyalkyl groups; R₄ is an alkyl group, an alkenyl group,a hydroxyalkyl, or an oligomer of hydroxyalkyl groups; and an alcoholselected from the group consisting of alkenes, cycloalkylenes andmixtures thereof.
 2. The chemical additive of claim 1, wherein the etheramine is present at from approximately 5% to 60% by weight of theadditive.
 3. The chemical additive of claim 1, wherein the ether amineis selected from the group consisting of ethoxylated ether amines,propoxylated ether amines, and combinations thereof.
 4. The chemicaladditive of claim 1, wherein the alcohol is present at fromapproximately 40% to 95% by weight of the additive.
 5. The chemicaladditive of claim 1, wherein the alcohol is a terpene alcohol.
 6. Thechemical additive of claim 1, wherein the alcohol is terpinol.
 7. Achemical additive for cleaning a wellbore and drilling equipmentconsisting essentially of:an alcohol selected from the group consistingof an alkene alcohol, cycloalkylenes and mixtures thereof; and a basefluid selected from the group consisting of esters, diethers, olefins,detergent alkylates and mixtures thereof.
 8. A chemical additive ofclaim 7 wherein said alcohol is about 20% to about 75% by weight of thechemical additive.
 9. A chemical additive of claim 7 wherein saidalcohol is a terpene alcohol.
 10. A chemical additive of claim 7 whereinsaid alcohol is terpinol.
 11. A chemical additive of claim 7 whereinsaid base fluid is about 25% to about 80% by weight of the chemicaladditive.
 12. A chemical additive for cleaning a wellbore and drillingequipment, comprising:an ether amine having the formula: ##STR4##wherein R₁ is a hydrocarbon group; R₂ is a hydrocarbon group; R₃ is analkyl group, an alkenyl group, a hydroxyalkyl group, or an oligomer ofhydroxyalkyl groups; R₄ is an alkyl group, an alkenyl group, ahydroxyalkyl, or an oligomer of hydroxyalkyl groups; and an alcohol; anda base fluid consisting of esters, diethers, olefins, detergent alkylateand mixtures thereof.
 13. The chemical additive of claim 12, wherein thebase fluid is present at from approximately 5% to 50% by weight of theadditive.
 14. The chemical additive of claim 12, wherein the ether amineis present at from approximately 5% to 60% by weight of the additive.15. The chemical additive of claim 12, wherein the ether amine isselected from the group consisting of ethoxylated ether amine,propoxylated ether amine, and combinations thereof.
 16. The chemicaladditive of claim 12, wherein the alcohol is present at fromapproximately 20% to 75% by weight of the additive.
 17. The chemicaladditive of claim 12, wherein the alcohol is a terpene alcohol.
 18. Thechemical additive of claim 12, wherein the alcohol is terpinol.
 19. Achemical additive for cleaning a wellbore and drilling equipment,comprising:an ether amine having the formula: ##STR5## a terpenealcohol, wherein R is a hydrocarbon group; n=2 or 3; m is an intergergreater than zero, wherein the ether amine is present at fromapproximately 5% to 60% by weight of the additive, wherein the terpenealcohol is present at from approximately 40% to 95% by weight of theadditive.
 20. A chemical additive for cleaning a wellbore and drillingequipment, comprising:an ether amine having the formula: ##STR6## aterpene alcohol; and a base fluid selected from the group consisting ofesters, diethers, olefins, detergent alkylates and mixtures thereof;wherein R is a hydrocarbon group; n=2 or 3; m is an interger greaterthan zero, wherein the ether amine is present at from approximately 5%to 60% by weight of the additive, wherein the terpene alcohol is presentat from approximately 20% to 75% by weight of the additive, and whereinthe base fluid is present at approximately 5% to 50% by weight of theadditive.